[Immunization of calves with a rabies vaccine from suckling mouse brain].

This paper summarizes the results obtained in a study on the duration of immunity in calves immunized with suckling mouse brain (SMB) rabies vaccine, supplemented with aluminum hydroxide. Rabies circulating antibodies were detected ten days after vaccination in 100% of the 31 vaccinated calves. They began to decrease 90 days after immunization. Of the 15 calves challenged one year postimmunization, 5 (33%) had no detectable antibodies at serum dilution 1:5, but all were protected against the challenge dose virus which killed 75% (3/4) of the non vaccinated controls. The results obtained suggest that SMB rabies vaccine can be used successfully to immunize calves aged from 7 days to 6 months. Since 15 to 20% of the cattle population of a country is less than one-year-old, the protection of this population against rabies with an inactivated vaccine would decrease the number of susceptible animals and facilitate both the vaccination procedures and the movement of animals from rabies-free areas to those where the disease is enzootic.